Dr. Horwitz's immediate career goals are twofold: to develop creative, physiologically-based approaches to the study of mechanisms underlying speech understanding in normal and impaired auditory systems; and to expand her skills and knowledge base through training activities available in the Medical University of South carolina's multi- disciplinary research training environment. Planned career development experiences include: a) collaborative research that bridges the disciplines of cochlear physiology, psychoacoustics and speech perception using behavioral as well as functional neuroimaging approaches; b) relevant course work, seminars, and independent studies with her sponsor and collaborators, and; c) implementation of the mentored research plan. The new and enhanced research skills Dr. Horwitz will acquire as a result of these activities should enable her to achieve her long-term career goal as a productive investigator integrating results from basic auditory research and applying them to the study of how listeners process and understand speech in their daily lives. The research project is designed to provide a better model of the contribution of the base of the cochlea to speech understanding in realistic listening environments for listeners with normal and impaired high-frequency hearing. Motivated by the fact that people with high- frequency hearing loss often complain of difficulty understanding speech beyond what might be expected due to the reduction in audible high- frequency speech information, four specific aims are proposed to test the hypothesis that high-frequency hearing loss diminishes the encoding of lower-frequency spectral and temporal information. Results should provide fundamental new information with direct relevance for the design and implementation of signal processing strategies to improve communication by listeners with high-frequency hearing loss.